Detection of honey adulteration by addition of fructose and glucose using near infrared transflectance spectroscopy

Samples of artisanal honey produced in Ireland over a number of harvests have been obtained directly from producers. Adulterant solutions containing both fructose and glucose at ratios of 0.7 : 1, 1.2 : 1 and 2.3 : 1 w/w were prepared. Honeys and adulterants were adjusted to a constant solids content. Visible and near infrared (400-2498 nm) transflectance spectra of the honeys were collected before and after adulteration at levels of 7, 14 and 21% w/w of each of the fructose-plus-glucose adulterant solutions. Chemometric analysis of the spectral collection by discriminant partial least squares regression (PLS1), k-nearest neighbours (k-NN) and soft independent modelling of class analogy (SIMCA) have been performed with a view to discriminating between the unadulterated and adulterated honey samples. Discriminant partial least squares regression proved to be the most accurate of these three methods.